Apparatus for estimating road friction coefficient

• US 6,543,278 B1
• Filed: 07/28/2000
• Issued: 04/08/2003
• Est. Priority Date: 07/30/1999
• Status: Expired due to Fees

• Current Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Original Assignee: Fuji Jukogyo KK (Subaru Corp.)
• Inventors: Kogure, Masaru
• Primary Examiner(s): PATEL, HARSHAD R
• Application Number:
  US09/628,683
• Time in Patent Office: 984 Days
• Field of Search: 731/46, 731/462, 73/9, 701/80, 701/74, 701/83, 701/82, 701/69, 701/88, 701/41, 701/89, 180/197
• US Class Current: 73/146
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• CPC Class Codes: B60W 2050/0033 Single-track, 2D vehicle model, i.e. two-wheel bicycle model

Abstract

A friction coefficient on road is estimated for vehicles. An actual vehicle of a specific vehicle operating parameter is calculated. A first reference value of the vehicle operating parameter on a road with a large friction coefficient is calculated based on vehicle operating model for the road with the large friction coefficient. A second reference value of the vehicle operating parameter on a road with a small friction coefficient is calculated based on vehicle operating model for the road with the small friction coefficient. A friction coefficient on road is estimated based on the relationship between the actual value and the first and the second reference values.

Claims

1. An apparatus for estimating a friction coefficient on a road for vehicles, the apparatus comprising:

a vehicle operating parameter calculator to calculate a vehicle operating parameter based on vehicle operating conditions;

a basic parameter calculator to calculate a basic parameter by inputting the vehicle operating parameter into a vehicle operating model;

a first reference value calculator to calculate a first reference value by inputting the vehicle operating parameter into said vehicle operating model for the road with the large friction coefficient;

a second reference value calculator to calculate a second reference value by inputting the vehicle operating parameter into said vehicle operating model for the road with the small friction coefficient; and

an estimator to estimate a friction coefficient on road based on the basic parameter, the first reference value and the second reference value.

2. The apparatus according to claim 1, wherein the vehicle operating parameter includes at least one of yaw rate and lateral acceleration.

3. The apparatus according to claim 2, wherein

said estimator estimates the friction coefficient on a road based on the basic parameter of the yaw rate, the first reference value of the yaw rate and the second reference value of the yaw rate when the vehicle operating condition satisfies a first predetermnined requirement.

4. The apparatus according to claim 2, wherein

said estimator estimates the friction coefficient on a road based on the basic parameter of the lateral acceleration, the first reference value of the lateral acceleration and the second reference value of the lateral acceleration when the vehicle operating condition satisfies a first predetermnined requirement.

5. The apparatus according to claim 1, wherein the basic parameter calculator forms an observer by the vehicle operating model to estimate the vehicle operating parameter as a basic parameter with feeding back of actual vehicle movements.

6. The apparatus according to claim 1, further comprising:

an adjuster to form a first Lissajous figure based on the basic parameter and the first reference value to calculate an area of the first Lissajous figure for the road with the large friction coefficient, and a second Lissaous figure based on the basic parameter and the second reference value to calculate an area of the second Lissajous figure for the road with the small friction coefficient,

and to adjust the friction coefficient based on a previously calculated friction coefficient and the areas of the first and the second Lissajous figures.

7. The apparatus according to claim 6, wherein

said estimator estimates the friction coefficient on a road based on the basic parameter of yaw rate, the first reference value of the yaw rate and the second reference value of the yaw rate when the vehicle operating condition satisfies a first predeterm.

8. The apparatus according to claim 4, wherein

said estimator estimates the friction coefficient on a road based on the basic parameter of front wheel slip angle, the first reference value of the front wheel slip angle and the second reference value of front wheel slip angle when the vehicle operating condition satisfies a second predetermined requirement.

9. The apparatus according to claim 8, wherein

said estimator estimates the friction coefficient on a road based on the previously calculated friction coefficient and area of the first and the second Lissajous figures.

10. The apparatus according to claim 1, wherein

said estimator estimates the friction coefficient on a road based on the basic parameter of front wheel slip angle, the first reference value of the front wheel slip angle and the second reference value of front wheel slip angle when the vehicle operating condition satisfies a second predetermined requirement.

11. An apparatus for estimating a friction coefficient on road for vehicles, the apparatus comprising:

a vehicle operating parameter calculator to calculate a vehicle operating parameter based on vehicle operating conditions;

a basic parameter calculator to calculate a basic parameter of one of yaw rate and lateral acceleration and another actual value of a front wheel slip angle;

a first reference value calculator to calculate a first reference value of one of the yaw rate and the lateral acceleration and a second reference value of the front wheel slip angle on a road with a large friction coefficient based on a vehicle operating model for the road with the large friction coefficient;

a second reference value calculator to calculate a third reference value of one of the yaw rate and the lateral acceleration and a fourth reference value of the front wheel slip angle on a road with a small friction coefficient based on a vehicle operating model for the road with the small friction coefficient; and

an estimator to estimate a first friction coefficient for a road based on the basic parameter and the first reference value on the road with the large friction coefficient and the third reference value on the road with the small fiction coefficient, and a second friction coefficient for a road based on the basic parameter and the second reference value on the road with the large friction coefficient and the fourth reference value on the road with the small fiction coefficient, either the first or the second fiction coefficient being employed according to predetermined requirements.

12. An apparatus for estimating friction coefficients on a road for vehicles, the apparatus comprising:

a vehicle operating parameter calculator to calculate a vehicle operating parameter based on vehicle operating conditions;

a basic parameter calculator to calculate a basic parameter of a front wheel slip angle;

a first reference value calculator to calculate a first reference value of a front wheel slip angle on a road with a large friction coefficient based on a vehicle operating model for the road with the large friction coefficient;

a second reference value calculator to calculate a second reference value of the front wheel slip angle on a road with a small friction coefficient based on a vehicle operating model for the road with the small friction coefficient; and

an estimator to estimate a friction coefficient on road based on the basic parameter and the first reference value and the second reference value.